Collet



July 11, 1933.

E. L. coNNELL K 1,917,752

COLLET Filed July 14, 1931 2 sheets-sheet 1 l 22 K' 2/ E l| /5 /0 /7 7/4' 20 VII/ll, I :K :kga /////A /8 f V7 /0 V6 1 www 30 3 July 11, 1933.E. CONNELL COLLET Filed July 14, 1951 .2 Sheets-Sheet 2 FII;

gmwm

Patented July 11, 1933 unirsi), STATES PArsar ePrice f EDWIN L. ooNNnLL,or Towson, MARYLArin, assrenon van Dolan ELECTRIC Toon COMPANY, 0FTOXVSON, I'IARYLANDy A CRPOEATION OF OHIQ COLLET Application. filed July14,

tube, having longitudinal slots extendingV from the alternate endsthereof. The ends are generally tapered or conical, to fit into seatshaving a corresponding taper. Due to the slots, the ends Vforni a.plurality of j aws,

which contract or expand relative to the axis of the collet, as oneofthe seats is moved longitudinally relative to the otherseat.

The general eobject of this invention is to provide a collet adapted togrip objects which vary through a considerable range of diameter, suchas the stems of automotivevalves, while positioning such object-s forrotation with the utmost degree of axial precision. i A more specicobject is to provide Va collet of such a` type that a minimumcircumferential surface or frictional area thereof will remain incontact with the collet retaining seat for all contracted or expandedpositions of the collet. j

Another objectris to providea collet of such a type as will minimize theerror in axial alignment kof objects gripped thereby, such errorresulting from the discrepancies in, the grinding of the tapered seat,the grinding of the tapered ends yof the collet or variations ininternal strength and characteristics of the metal of the gripping` jawslof the collet.

Another obj ect is to provide a collet where'- in the contact surfacesbetween the collet and collet seat will approach radial alignment withthe points of contact between the work gripping surfaces of the colletand the work.

Further objects of this invention will become apparent from thespecification, reference being had to a preferred embodiment illustratedin the drawings, and the essentialy features thereof will be set forthin the claims. f

Referring again to the drawings, wherein l illustrate a preferredforni'of myimproved collet, Fig. 1 is a longitudinal section 1931. sensino. sedere.'

through my collet mounted yin a spindle mechanism, and illustratesmyimproved collet in use.; Fig. 2 is a perspective'of my improved collet;Fig. 3 is an end elevation of my. improved collet in its expandedposition Fig. 4 is al view similar to 3 but illustrating the collet in acontracted position g, Figs. 5, 6

and are transverse sections, as indicated byf the lines 5 5, 6 6 and 7 7of Fig. 2, respectively; Figs. 8 and 9 are diagrammatic views and areillustrativeof the type collet formerly in use, Figs. 10 and 11 arediagrammatic views, similar to the views illustrated in Figs. 8 and 9,but illustratmg my improved collet; 12 isa perspective viewof a modifiedform of my improved collet; Fig. 131s an end elevation of the colletillustrating' the collet in its expanded position; Fig. 1d isan endelevation illustrating the collet in a con'- tracted position; Figs. 15,16 and 17 are transverse sections Vthrough the Aform of colletillustrated in Fig. 12, and are indicated by vthe lines, 1.5 15, 16-16and 17 17, of Fig. V1.2, respectively. `Fig. 18 is a diagrammatic viewsimilar to Fig. 10, but illustrating the iorm of collet shown in Fig.12.

Heretofore, collets ofthis type. comprised,

tubingcut to the required length and then slotted lengthwise from theopposite ends thereof. The alternate slots were arranged to breakthroughalternate ends of the blanks, forming a series of open ended slots.r`Grenerally there were three slots extending'- from each end of thetube, thereby forming three arcuate jaw sections on each end. Tliecollet ends or jaw sections were ground to the taper required to coactwith the collet seat, and were then hardened. lnV such constructions thearcuate. jaws, the outer or seat engaging surfaces were-of aconsiderable arcu# ate length, and as the seats werek broughtto getlierto contract the jaws, only the edges of each vjaw adjacent the slotsVcontacted with the seats, while the inner surface of each jaw contactedwitlrthe worl; only adjacent its center portion or intermediate theslots. The

grinding of both the collet jaws and the col# ieuV small, neverthelesscaused inaccuracy in the axial alignment of the work gripped by thecollet jaws. Likewise, the internal strength and characteristics of thematerial in one collet jaw varied from that in anotherVV collet jaw,with the result that when the collet was contracted, one jawk was oftenmore exible than the others, and thereby caused further inaccuracies inthe axial alignment of the work.

It is to be conceded that even though the utmost degree of care is usedin manufacturing the collet, inaccuracies such as those pointed outabove will sometimes be present. However, I find that it is possible tominimize, if not, for all practical purposes, eliminate the inaccuraciesin axial alignment of the work, due to the discrepancies or errors inthe collet itself. I iind that this is accomplished by decreasing thearcuate area of the collet jaws without increasing their number, and Ipropose to accomplish this by flattening or undercutting a portion ofthe jaws adjacent the slots. This materially reduces the distancebetween the points of contact of a jaw with the seat, and lessens oreliminates for practical purposes, the distance separating the centerportion of the jaw with the collet seat, bringing the points of contactloetween tlie jaw and the seat relatively close to a radial linepassing' through the point of contact between the jaw and the work. Ifind that by so constructing my collet the accuracy of accuratealignment of work gripped thereby is greatly enhanced. v

Referring again to the drawings, and especially to Fig. 1, where I showmy improved collet in use, the collet itself is generally indicated at10, and is slidably mounted in a suitable sleeve 12, which has acontracted con ical inner end surface member 14 rigid therewith, thelatter arranged to coact with the bevelled jaw portions 15 of thecollet. Slid` ably mounted in the sleeve 12 is a second sleeve 16,having a conically formed inner surface 17 adapted to coact with thebevelled surface 18 of the collet. A suitable plunger 19, threaded intothe sleeve 12, urges the sleeve 16 against the collet, bringing thebevelled surfaces 18 and 17 together, thereby contracting the ends ofthe collet. The plunger 19 is provided with a suitable hand wheel 20, bymeans of which it may be rotated within the sleeve 12, to bring thesleeve toward or away from the collet as desired. The sleeve 12 is inturn rotatably mounted in a ysuitable carriage or head 21, which isprovided with the usual feeding and indexing means, whereby the worksuch as an automotive valve 50, may be placed in proper relation to atool, such as a grinding wheel, (not shown). The sleeve 12is providedwith a suitable pulley 22, rigidly secured thereto, by means of whichthe sleeve with its associated collet 10 and Work 50 maybe rotated. f

'at each end thereof a` series of clamping jaws 82. To increase theflexibility of the body of the collet and enable the jaws 32 to becontraced with a minimum amount of distortion of the collet itself, Iundercut the inner and outer surfacesA of the collet interine- A diateits ends, as indicated at 33 and 31, re-

spectively, in Fig. 7. The inner surfaces 37 of the jaws 82'arearcuately ground relative to the axis of the collet, while the outersurfaces of the jaws are tapered, as indicated at 36, by a grindingoperation and are so tapered as to be in accurate axial alignment withthe axis of the collet and are arranged to contact with the colletclamping seatsL 1st and'17.

`rilo decrease the error in the alignment of the worlr gripped by thecollet, due to the iuaccuracies introduced into the collet by thegrinding operation, and the errors due to valuations in the internalstrength and characteristics of the metal which comprises the jaws ofthe collet, I flatten the aws adjacent the slots, as shown'at et() inFigs. 2, and 4l. Theseflattened portions are tapered at a` more acuteangle relative to the axis of the collet than is the seat taper 36,thereby iestricting the contact between the jaws and the seats 14 and 17to the now restricted tapered portions 36. l

j The advantages of this construction are brought out in thediagrammatic Figures 8 to 10, inclusive. In tl'iesediagrams Figs. S and9 are representative of the ordinaryype lhcpllet, wihile igs. 10 and 11are correspondg representations of my improvedv collet. Figs. 8 and 10diagrammatically represent an end or view of the jaws of the oidinarypllllgtilinicCiigj'oved collet, respectively. I i. D ie jaws arearranged for the same maximum outside diameter in the lxpanded position.The tapered surfaces of Hemjiuesepresented at 39 and the i l c l myimproved collet jaw is indicated at 40. Figs. 9 and 11 are diigrammaticillustrations or views of my iiiiproved collet and the ordinary colletrcspectively, illustrating their positions ielative to a seat 45 and aApiece of work lV. a Fig. 9 reiresents the ordinary collet, having jawsA, B and C, while Fig. 11 represents my improved collet, having jaws A,B and C. Each of the latter being provided with flattened surfaces 10.In these figures the jaws A and A are shown distorted, due either toerrors in grinding of the jaws or seats or'the difference in theflexibility of the metal comprising thejaws.` The points of contactbetween the jaw A and the seat 15 l lax ing the width of the slots.

is indicated at a and in Fig. 9 and a and o in Fig. 11, while the pointof contact between the jaw and the work is indicated at (l in bothfigures. In Fig. 9 it will be noted that due to errors in grinding orthe flexing of the metal in the jaw A, that the distance e `between thejaw 'and the collet is considerably less than the distance j between thejaws B and C and the collet seat. This throws the center of the work TWaway from the axis ofrotation If and towards the jaw A to the point Y,thereby throwing the work out of axial alignment with the collet. As theoperation performed on the work, generally a cutting or a grindingoperation, will be coaxial with the axis of rotation of the collet andits spindle, the result is that this operation or cut performed on thework is not coaxial with that part of the work gripped by the collet.

in my improved collet, I have lessened and eliminated for practicalpurposes, the inaccuracies in alignment, due to the errors in g inningor flexibility of the collet. In Fig. 11i-'lt will be noted that thepoints of contact between A and B, between the collet and the seat 15,have been brought relatively close together, and by reducing the bridgebetween these points I have greatly reduced the 'tendency of the jaw Ato flex. Likewise, because the points of contact have been broughttogether, the distances c and ,f h ve been, for all practical purposes,eliminated. Hence, the. center of the work W will be coaxial with thecenter of rotation of the collet and seat 15.

Fig. 12 illustrates a modified form of my improved collet, in which thejaws adjacent the slot are undercut, rather than flattened. This ishighly desirable if the collets were used in conjunction with certaintypes of chucks, wherein a collet having flat surfaces would have somuch metal cut away at the edge of the jaws that it slips through theopening at the front end of the chuck. I-Iowever, by undecutting thecurved surface of the jaws, the width of the spherical seats may bevaried, as desired, without increas- V This modified form of the colletis best illustrated in Figs. 12 to 18, inclusive, and comprises a. tube30a, having a s .ries of slots 31a, cut in the walls thereof, thealternate slots extending through alternate ends of the collet, formingat each end thereof a series of clamping jaws 32o. The inner surfaces37a of the jaws 32a are accurately ground relative to the axis of thecollet, while the outer surfaces of the jaws are tapered, or otherwiseshaped to lit the seats as indicated at 36a, by a grinding operation,and are so formed as to be in accurate axial alignment with the axis ofthe collet.

ln'this modified form of collet, I prefer to decrease the error inalignment of the work,

due to inaccuracy introducedin the grinding operation, as heretoforementioned, by cutting away the surfaces of the aws adjacent the slots,instead offiattening the jaws, as heretofore described and shown inconnection with Figs. 1 to 11, inclusive. The cut away or low portionsof the jaws are shown at-() in Figs. 12, 13, 14 and 18, and lie adjacentthe slots which pass through that end of the collet. Intermediate thelow portions of each jaw and midway between the adjacent slots is abridgel of metal l, which bridge is bevelled or shaped to conform andcontact with the seats l14 and 17 of the collet clamping mechanism. 'Ihelow portions are. of a sufiicient depth to prevent contact betweenk thejaws and the collet seats, except at thebridge portions 51, in anyexpanded or contracted position of the collet.

T he ad rvantage of this` construction is brought out in thediagrammatic Figure 1S. This figure diagrauunatically represents themodified form of collet in use. The seat is indicated at 60 and the workat IV, while the low portions of the jaws are represented at 50. It willbe noted from this figure that the collet o contacts' with the seat 60only at the bridge portion 51, andthe bridge portions 51 are of such awidth that the points of contact a and o, between any collet jaw i andthe seat are relatively close together and substantially in line withthe point of Contact f between the work and the inner seat of thecollet. Hence, by reducing the width of the bridge between the points ofcontact of the collet with the collet seat, I have greatly reduced thetendency of the jaw A to flex. Likewise, because the points of contacthave been brought together', the alignment of thework gripped by thecollet is greatly enhanced, as heretoforedescribed, in connection withthe collet shown in Figs. 1 to 7, inclusive.

It is to be noted that in the form of collet shown in Figs. 12 to 18,bridge portions 51 of the collet seat may be increased or decreased inwidth as desired, without affecting the width of the slots 31a, while,in the instance of the form of collet shown in Figs. 1 to 11, in orderto. decrease the width of the bridge portions by flattening theends ofthe collet, it would, beyond a certain limit, increase the width of theslot 31 of the collet, thereby decreasing the effectiveness of thecollet by cutting away too much metal from the ends thereof.

From the foregoing, it will be seen that I have provided a collet, inwhich thel ordinary errors, due to inaccurate grinding and if'ariationsininternal structure of the metal of the collet jaws, will not affectthe axial alignment between the work and the axis of rotation of thecollet.

I claim:

1. A collet for use with opposed relatively movable sockets havingsubstantially conical internal seats, comprising a tubular member havingslots extending longitudinally therethrough from opposite ends andextending to a point a fixed distance from the other end of the member,said member having the ends thereof bevelled to correspond with theseat, and wherein the bevelled portions are cut away on the outersurface of the collet adjacent the open ends of the slots, to reduce theWidth of the seat contact area of the collet for all diameters ot work.

2. A chucking member of the type described, adapted to be retainedbetween relatively movable sockets having substantially conical seats,said member comprising a tube having slots, each succeeding slotextending through alternate ends ot the tube, substantially conicalsurfaces adjacent the ends et the tube and adapted to coact with theseats and wherein the outer conical surfaces of the tube areflattened'longitudinally on each side of the open ends of the slots andin a plane normal to the plane of the slot and intersecting the axisextended of the tube and wherein the flat areas are arranged to remainout of Contact with the conical socket seat for all operating positionsof the collet.

collet ot the type used to grip various diameters of Work and which isused with opposed relatively movable sockets one of which has asubstantially conical seat, said collet comprising a tubular memberhaving slots extending longitudinally therethrough :trom one end andnearly the entire length thereof, and forming a series of jaws on oneond of the member, the outer periphery of each of said jaws formed witha plurality of longitudinally extending surface areas of differentcharacteristics, the surface areas adjacent the slots depressed toremain out of contact with the conical sockets for all diameters 01":Work, and the median surface raised to contact With the conical seat forall diameters of work.

ln testimony whereof, I hereunto affix my signature.

EDVTN L. CONNELL.

